One of the inventors has already proposed an apparatus of the aforementioned kind wherein a long strip of band of plate material is fed longitudinally between a plate-form die and a roller, as disclosed in U.S. Pat. No. 3,792,602. The long strip or band of plate material has a relatively high elasticity. For example, copper alloy, stainless steel or nickel silver may be used. The plate material is brought into contact with a plate surface portion of the plate-form die, the plate surface portion being sharpened at a leading end portion. A pressure roller means is arranged so that a single roller is rolled with a reciprocating stroke corresponding to the plate surface portion of the plate-form die for pressing the long strip or band of plate material against the plate surface portion. Thus, this type of apparatus is advantageous in that the plate of irregular sectional shape can be manufactured without the waste of material which attends forming by cutting.
However, since the pressure roller means of the foregoing prior art apparatus comprises a single pressure roller, and the single pressure roller has a reciprocating stroke corresponding to the plate surface portion of the plate-form die for pressing the long strip or band of plate material, the prior art apparatus is inconvenient in that if the travel speed of the pressure roller is increased in order to increase productivity, a force applied to a driving transmission mechanism for the roller becomes excessive, and the mechanism becomes liable to be damaged. Further, the prior art apparatus is inconvenient in that if the travel speed of the pressure roller is increased the rolling speed of the pressure roller is also increased, thereby causing slippage between the pressure roller and the plate material as the travel direction of the pressure roller is reversed, which slippage results in a seizure phenomenon. Furthermore, the prior art apparatus is inconvenient in that is the pressing process using a single pressure roller, the plate material is pressed against the plate-form die at a single portion, so that the plate material is liable to be displaced in its width direction. Consequently, it is difficult to obtain a precise size of the product in the width direction of the plate of irregular sectional shape.